This is an interesting subject. There have been discovered very large (up to around 100 kpc) hot (10^7 K) intergalactic gas clouds within galaxy clusters.
A simple calculation based on the density of the gas clouds in question and the emission rate of the hot gas shows the gas clouds should have cooled and formed stars/galaxies.
There are two anomalies. What is the source of energy to heat a very large gas cloud evenly. As noted in this paper AGN and gas in flow will heat the gas cloud unevenly. Also in the case of a gas flow hypothesis there is a mass problem as one needs too much infall gas to continually flow into the original gas cloud.
The second and related problem, is why does the gas cloud not cool.
Interesting also is the mass of the intergalactic cluster gas is approximately the same as the mass of the visible matter (stars) in the cluster's galaxies.